The Mechanics of Diving

     Diving is basically the art of leaping from a height and entering the water. In doing diving the body has first to overcome inertia, that is the force of gravity acting on its mass and keeping it in the same spot, at rest. A diver standing on a board will remain there forever unless some force is exerted upon him; either from his legs and springing muscles or from someone pushing him from behind. When the force used to overcome the initial inertia is expended the body, now in mid-air, is pulled with ever-increasing speed to the water below by the same force of gravity.

Diving gravity is the attractive force by which bodies tend to move to the centre of the earth. Diving gravity pulls bodies towards the earth with a uniform acceleration of 32 feet per second per second. A body falling from rest will travel 16 feet in the first second, 48 in the next and 80 in the third. The total distance fallen in 3 seconds will be 144 feet (16 plus 48 plus 80). The size of the body falling has no effect on its speed. A four-stone weight dropped from a 10-metre diving board simultaneously with a four-ounce weight hits the water below at the same instant. A twelve-stone adult diver falls at the same speed as a boy diver weighing five stones, and takes exactly the same time.

However, this increasing diving acceleration gives a body greater speed the greater the height from which it falls. As the momentum of the diver's body (which may be regarded as a measure of the impact with which it hits the water), is its mass multiplied by its speed, the higher the dive the harder the body hits the water. The time of falling in diving can only be influenced by air resistance. A feather has for its weight a very large surface area which, due to friction with the air, slows its fall If a feather and a steel ball bearing were dropped inside a vacuum tube they would fall at exactly the same rate and take the same time, there being no air inside the tube to slow down the rate of fall of the feather. Having regard to the comparatively small heights from which diving is performed and to the make-up of the human body, air resistance is negligible.